Line cards are often used to process data on a network line. Each line card acts as an interface between a network and a switch fabric. The line card may convert the data set from the format used by the network to a format for processing. The line card also may perform necessary processing on the data set. This processing may include further translation, encryption, error checking, and the like. After processing, the line card converts the data set into a transmission format for transmission across the switch fabric.
The line card also allows a data set to be transmitted from the switch fabric to the network. The line card receives a data set from the switch fabric, processes the data set, and then converts the data set into the network format. The network format can be asynchronous transfer mode (ATM) or a different format.
When a half-duplex processor based line card is used, two network processors are needed to achieve full duplex network communications. One network processor may be used for inbound traffic and the other network processor may be used for outgoing traffic. Inbound data traffic is typically traffic from the media to the switch fabric, while outbound traffic is typically data traffic from the switch fabric to the media. The switch fabric provides the interface between the line card and the network. Each network processor can communicate with the switch fabric in only one direction. When data buffers in either the line card and/or the switch fabric overflow, large round trip latency is introduced to communicate flow control information to the line card and/or the switch fabric to adjust the data flow.